Problem: Rearrange the equation so $b$ is the independent variable. $a-7=3(b+2)$ $a=$
Explanation: To arrive at a correct equation, we have to solve the equation for $a$. $\begin{aligned}a-7&=3(b+2)\\\\ a&=3(b+2)+7\\\\ a&=3b+6+7\\\\ a&=3b+13\end{aligned}$ The following equation is rearranged so $b$ is the independent variable: $a=3b+13$